You're hitting the Cape during high tourist season. Prepare for crowds and choose your arrival/departure outside peak hours. Word to the wise
Best informational website overall:
http://www.capecodchamber.org/
Bike trail specific info:
http://www.massbike.org/bikeways/capecod.htm
There is so much to do and see on the Cape, and much of it based on personal preference, that it's hard to recommend certain places or restaurants. I never had trouble finding vegetarian food; don't know how difficult vegan would be, but I imagine
not too hard.
Have fun!